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The June 23, 2011 M7.3 earthquake is located in the central part of the 1957 rupture zone. In 1986, a portion of the western half of the 1957 zone failed in an earthquake of magnitude 7.9. In 1996 another magnitude 7.9 earthquake appear to have completed re-rupture of the western end of the 1957 zone, immediately westward of the 1986 region. No other major (magnitude 7 or greater) earthquakes occurred within the 1957 rupture zone up until this event. The depth and faulting type of the mainshock is consistent with it being an intraslab earthquake, i.e. occurring inside the subducting Pacific plate rather than on the plate interface.

Last Modified: May 13, 2020